Before the update, my custom ActionListener I have registered within the faces-config.xml was called after clicking the button. After the update, this is no the case. I have traced it down to the fact, that the commandButton's decode method is not called. It seems to have something to do with the tabPanel surounding the form. If I remove the TabPanel, everything works like normal.

After your reply, I had a view more tries this morning. At the beginning I could not recreat the problem. But after a view changes in the attributes, I came out with these to code snippes. With the first one, everything is working fine, the second one has the descriped behavour.